Existing commercial jet transport aircraft include multiple turbofan engines, each coupled to a starter/generator. The starter/generator is used both to start the turbofan engine and extract electrical power from the turbofan engine once the turbofan engine is started. The extracted electrical power is then routed to electrical systems on the aircraft.
Existing starter/generators create heat that must be dissipated to prevent overheating and subsequent system failure. FIG. 1 illustrates a typical air-cooled oil cooler 20 (i.e., a heat exchanger) designed for this purpose. The heat exchanger 20 receives hot cooling oil from the starter/generator via a hot oil supply 31, and returns cooled oil to the starter/generator via a cool oil return 32. Within the heat exchanger 20, cold air cools the initially hot oil. The cold air can be received from a cold air supply 51, which is coupled to an air source, for example, an air scoop located behind the fan of the turbofan engine. A warm air return 52 returns air warmed by the oil, for example, by reintroducing the air to the fan flow, or by dumping the air overboard the aircraft.
The foregoing arrangement has proved suitable for aircraft having a single starter/generator associated with each turbofan engine. However, newer aircraft are placing greater electrical demands on the turbofan engines and accordingly include multiple starter/generators associated with each turbofan engine. One approach for cooling the additional starter/generators is to provide a heat exchanger generally similar to the one shown in FIG. 1 for each starter/generator. However, this can dramatically increase the weight of the heat exchanger system and is therefore not satisfactory. As a result, there is a need for a lighter weight, more efficient heat exchanger system.